The present invention relates to a rear-view mirror with a wide viewing angle and reduced image distortion, which is accordingly adapted for external mirror for vehicles.
With a mirror of this type it is possible to achieve a viewing angle of up to 85° without unacceptable distortion of the image. Furthermore, a single uninterrupted image is provided over the entire reflecting surface.
Conventional flat or slightly curved rear-view mirrors for vehicles installed outside the cabin do not allow to have a wide viewing angle, which is usually only approximately 20° or even less.
With a reflecting device of this type the driver is unable to visually detect the presence of, for example, overtaking vehicles, because from a certain point onwards they enter a blind spot which is not covered by the viewing angle of the mirror.
This causes considerable danger, since the driver may be induced to perform maneuvers which he believes to be safe and may instead make him collide with another vehicle which is very close but not visible to him.
In order to obviate this drawback, mirrors have been designed which have differentiated regions providing flat surfaces next to spherical or aspheric surfaces.
The use of these mirrors has encountered many limitations, because the reflected image is reduced and distorted.
In particular, a reduced image does not allow to evaluate the distance of the object being viewed and does not allow to assess its approach speed.
These problems have therefore led to statutory provisions which forbid the use of these mirrors on cars and commercial vehicles unless they are combined with conventional flat mirrors, known as aspheric mirrors.
Such mirrors achieve a maximum viewing angle of 42°, but they provide two different images: a normal one on the flat mirror and a reduced and distorted one in the outermost aspheric part.
In order to obviate this, innovative technologies, such as the use of miniature TV cameras or other concepts such as a prismatic mirror, have recently been developed; they are interesting but complicated and expensive to apply.